A Navy archaeologist and his crew are digging out a cave on San Nicolas Island that seems likely to have sheltered the woman made famous by the 1960 award-winning book.

Rene Vellanoweth of Cal State L.A. shows a cave on San Nicolas Island where… (Steve Schwartz, U.S. Navy )

The yellowing government survey map of San Nicolas Island dated from 1879, but it was quite clear: There was a big black dot on the southwest coast and, next to it, the words "Indian Cave."

For more than 20 years, Navy archaeologist Steve Schwartz searched for that cave. It was believed to be home to the island's most famous inhabitant, a Native American woman who survived on the island for 18 years, abandoned and alone, and became the inspiration for "Island of the Blue Dolphins," one of the 20th century's most popular novels for young readers.

The problem for Schwartz was that San Nicolas, a wind-raked, 22-square-mile chunk of sandstone and scrub, has few caves, all of them dank, wet hollows where the tides surge in and nobody could live for long.

Year after year, he scoured the beaches and cliffs, drilled exploratory holes, checked the old map, pored over contemporary accounts and conferred with other experts, all in vain. If he could find the cave, he could find artifacts — clues that would flesh out the real-life story that inspired Scott O'Dell to pen the 1960 novel that won the Newbery Medal and became required reading in many California schools. More than 6.5 million copies are in print and teachers frequently assign it between the fourth and seventh grades.

If he found the cave, he might solve mysteries about the "Lone Woman of San Nicolas" and her Nicoleño tribe, which was left devastated by a massacre in 1814 by sea otter hunters from Alaska.

With the help of recently unearthed notes written in a fine script by a 19th century government surveyor, Schwartz now believes he's found it.

"We're 90% sure this is the Lone Woman's cave," Schwartz told several hundred fellow researchers last week at the California Islands Symposium in Ventura. Further excavation is necessary, he said, adding that a crew of students has painstakingly removed about 40,000 buckets, or a million pounds, of sand from a cavern at least 75 feet long and 10 feet high.

In a separate discovery that also could shed light on the Lone Woman and her people, researchers stumbled across two redwood boxes poking through a steep, eroding cliff. The containers, probably made from recycled canoe planks and held together with the tar that washes onto island beaches, hold more than 200 stone blades, harpoon points, bone fishhooks and other implements.

"We find amazing stuff every time we go to the Channel Islands, and this may be the most amazing find of all," said Jon M. Erlandson, a University of Oregon archaeologist who has explored the islands for more than 30 years.

It may never be known just who left the cache of tools, he said, but "it's at least a reasonable hypothesis" that it was the Lone Woman, who is known to have stashed useful items at a number of places around the island.

About 60 miles off the coast, San Nicolas is a lonely Navy base dotted with installations designed to track missiles. It also has more than 540 known archaeological sites, some with evidence that people have lived on the island for more than 8,000 years.

For many Nicoleños, life ended in the early 1800s. Russian fur traders brought groups of Alaskan sea otter hunters to San Nicolas, where they engaged in repeated fights with native men over women and furs. The Nicoleño population dwindled from perhaps 300 to a few dozen, dropping most sharply after a particularly savage battle in 1814.

By 1835, the few Nicoleños left were struggling. Whether motivated by compassion or a need to increase the ranks of mission laborers, Franciscan fathers from the mainland sent a ship for them. All but one made the trip to the mainland aboard the Peor es Nada, loosely translated as "Better than nothing."

The holdout came to be known as the Lone Woman. According to legend, she jumped overboard and swam for shore when she frantically realized that her baby had been left behind. Less romanticized theories hold that she told the captain she'd show up with her child but a sudden storm forced him to shove off without her.

What's known is that a solitary woman lived in the sand and fog of San Nicolas for the next 18 years. On the mainland, her legend grew. A time or two, fishermen reported seeing a fleeting figure on the deserted island. In 1850, a padre at the Santa Barbara Mission commissioned a sea captain to find her.

The captain sailed to the island but found nothing to indicate the woman was still alive. However, his account of the plentiful seals and sea otters piqued the interest of George Nidever, a Santa Barbara rancher and fur trader. In 1852, Nidever found footprints on the beach. The next year, he found the Lone Woman.

"The old woman was of medium height but rather thick," he later reported. "She must have been about 50 years old but she was still strong and active. Her face was pleasing, as she was continuously smiling. Her teeth were entire but worn to the gums."